What are the boiling point of a solution prepared by dissolving 2.40g of biphenyl(C^12H^10) in 75.0g of benzene? The molecular weight of biphenyl is 154..
All of the above is ok except the last line. Solve for delta T, than add to the normal boiling point of benzene</> to find the new boiling point. The adding to 100 is for water; this is a not a water solution.
moles biphen = grams/molar mass
Solve for moles.
m = moles/kg solvent.
Solve for m = molality
delta T = Kb*m
Solve for delta T, then add to 100 to find the new boiling point.
To calculate the boiling point of the solution, we need to use the equation:
ΔTb = Kb * m
Where:
ΔTb = boiling point elevation
Kb = molal boiling point elevation constant (specific to the solvent)
m = molality of the solution
To find the molality (m) of the solution, we first need to calculate the number of moles of the solute (biphenyl) and the solvent (benzene).
Number of moles of biphenyl:
Mass of biphenyl = 2.40 g
Molar mass of biphenyl = 154 g/mol
Number of moles of biphenyl = mass / molar mass
Number of moles of biphenyl = 2.40 g / 154 g/mol
Number of moles of benzene:
Mass of benzene = 75.0 g
Molar mass of benzene = 78.12 g/mol
Number of moles of benzene = mass / molar mass
Number of moles of benzene = 75.0 g / 78.12 g/mol
Next, we calculate the molality (m) of the solution:
Molality (m) = moles of solute / mass of solvent in kg
Mass of solvent = 75.0 g = 0.075 kg
Molality (m) = (moles of biphenyl) / (mass of benzene in kg)
Molality (m) = (2.40 g / 154 g/mol) / 0.075 kg
Now that we have the molality, we can calculate the boiling point elevation (ΔTb). We need to use the molal boiling point elevation constant (Kb) for benzene.
The Kb for benzene is 2.53 °C/m (degrees Celsius per molal).
ΔTb = Kb * m
ΔTb = 2.53 °C/m * molality (m)
Finally, we can calculate the boiling point of the solution:
Boiling point of solution = boiling point of pure solvent + ΔTb
The boiling point of pure benzene is 80.1°C.
Boiling point of solution = 80.1°C + ΔTb
Substitute the value of ΔTb into the equation to find the boiling point of the solution.
To determine the boiling point of a solution, we need to calculate the change in boiling point caused by the dissolved solute. This can be done using the formula:
ΔTb = Kbm
where ΔTb is the change in boiling point, Kb is the molal boiling point elevation constant, and m is the molality of the solution.
To calculate the molality (m), we need to find the moles of solute and the mass of the solvent.
Moles of biphenyl = mass / molecular weight = 2.40g / 154 g/mol = 0.0156 mol
Mass of benzene = 75.0g
Molality (m) = moles of solute / mass of solvent (in kg)
mass of benzene in kg = 75.0g / 1000 = 0.075 kg
m = 0.0156 mol / 0.075 kg = 0.208 mol/kg
Next, we need the molal boiling point elevation constant (Kb). The Kb value for benzene is approximately 2.53 °C/molal.
Now we can calculate the change in boiling point (ΔTb):
ΔTb = Kb * m = 2.53 °C/molal * 0.208 mol/kg = 0.526 °C
The boiling point elevation is the change in boiling point. Therefore, the boiling point of the solution will be higher than the boiling point of pure benzene by ΔTb.
To find the final boiling point, you need to add ΔTb to the boiling point of pure benzene. The boiling point of pure benzene is approximately 80.1 °C.
Final boiling point = boiling point of pure benzene + ΔTb = 80.1 °C + 0.526 °C = 80.626 °C
Therefore, the boiling point of the solution prepared by dissolving 2.40g of biphenyl in 75.0g of benzene is approximately 80.626 °C.